How do I measure duration in seconds in a shell script?

Shell Problem Overview

I wish to find out how long an operation takes in a Linux shell script. How can I do this?

Shell Solutions

Solution 1 - Shell

Using the time command, as others have suggested, is a good idea.

Another option is to use the magic built-in variable $SECONDS, which contains the number of seconds since the script started executing. You can say:

START_TIME=$SECONDS
dosomething
ELAPSED_TIME=$(($SECONDS - $START_TIME))

I think this is bash-specific, but since you're on Linux, I assume you're using bash.

Solution 2 - Shell

Use the time command. time ls /bin.

Solution 3 - Shell

Try following example:

START_TIME=$SECONDS
# do something
sleep 65

ELAPSED_TIME=$(($SECONDS - $START_TIME))

echo "$(($ELAPSED_TIME/60)) min $(($ELAPSED_TIME%60)) sec"    
#> 1 min 5 sec

Solution 4 - Shell

Many of the answers mention $SECONDS, but that variable is actually even better than they realize:

> Assignment to this variable resets the count to the value assigned, and the expanded value becomes the value assigned plus the number of seconds since the assignment.

This means you can simply query this variable directly at the end of your script to print the elapsed time:

#!/usr/bin/env bash

# Do stuff...

echo "Script finished in $SECONDS seconds."

You can also time smaller sections like so:

#!/usr/bin/env bash

# Do stuff

SECONDS=0

# Do timed stuff...

echo "Timed stuff finished in $SECONDS seconds."

Solution 5 - Shell

Here is the script to find the time elapsed in milliseconds. Replace the sleep 60 line with the code you want to execute.

a=0
while [ $a -lt 10 ]
do
    START_TIME=`echo $(($(date +%s%N)/1000000))`
    sleep 3
    END_TIME=`echo $(($(date +%s%N)/1000000))`
    ELAPSED_TIME=$(($END_TIME - $START_TIME))
    echo $ELAPSED_TIME
    if [ $a -eq 10 ]
    then
        break
    fi
    a=`expr $a + 1`
done

Solution 6 - Shell

Just to help anyone like me that receive an error:

 arithmetic expression: expecting primary: "-"

Check your shellscript that shall start with:

#!/bin/bash

Cheers!

Solution 7 - Shell

GNU time

I'm also a big fun of the GNU time command: https://www.gnu.org/software/time/ which offers some important options compared to the time Bash built-in.

Sample usage:

env time --format '%e' --output time.log sleep 1

Output:

1.00

Explanation:

env: to find /usr/bin/time instead of the Bash built-in
--format '%e': print time in seconds, see man time.

This is often what I want when benchmarking: a single number rather than minutes + seconds.

And an important pattern I often use is:

bench-cmd() (
  logfile=time.log
  echo "cmd $@" >> "$logfile"
  printf 'time ' >> "$logfile"
  bench_cmd="env time --append --format '%e' --output '$logfile' $@"
  eval "$bench_cmd"
  echo >> "$logfile"
)

rm -f time.log
bench-cmd sleep 1
bench-cmd sleep 2
bench-cmd sleep 3
cat time.log

GitHub upstream.